Journal of Bionic Engineering ›› 2022, Vol. 19 ›› Issue (5): 1422-1438.doi: 10.1007/s42235-022-00203-2

• • 上一篇    下一篇

Effects of Morphological Integrity of Secondary Feather on Their Drag Reduction in Pigeons

Qian Li1, Huan Shen1, Qingfei Han1, Aihong Ji1, Zhendong Dai1, Stanislav N. Gorb2   

  1. 1 Institute of Bio-Inspired Structure and Surface Engineering, College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, China  2 Department of Functional Morphology and Biomechanics, Kiel University, Am Botanischen Garten 9, 24118 Kiel, Germany
  • 收稿日期:2021-12-28 修回日期:2022-04-09 接受日期:2022-04-11 出版日期:2022-09-10 发布日期:2022-09-24
  • 通讯作者: Aihong Ji E-mail:meeahji@nuaa.edu.cn
  • 作者简介:Qian Li1, Huan Shen1, Qingfei Han1, Aihong Ji1, Zhendong Dai1, Stanislav N. Gorb2

Effects of Morphological Integrity of Secondary Feather on Their Drag Reduction in Pigeons

Qian Li1, Huan Shen1, Qingfei Han1, Aihong Ji1, Zhendong Dai1, Stanislav N. Gorb2   

  1. 1 Institute of Bio-Inspired Structure and Surface Engineering, College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, China  2 Department of Functional Morphology and Biomechanics, Kiel University, Am Botanischen Garten 9, 24118 Kiel, Germany
  • Received:2021-12-28 Revised:2022-04-09 Accepted:2022-04-11 Online:2022-09-10 Published:2022-09-24
  • Contact: Aihong Ji E-mail:meeahji@nuaa.edu.cn
  • About author:Qian Li1, Huan Shen1, Qingfei Han1, Aihong Ji1, Zhendong Dai1, Stanislav N. Gorb2

摘要: Flight feathers of birds interact with the air flow during flight. How the observed low drag and high lift values at wind speeds from 9.0 to 19.8 m/s can be achieved due to the feather aerodynamics remains unknown. In the present paper, we tested and compared morphological changes, drag reduction and flow visualization results of intact, damaged, and artificial feathers at different wind speeds in a wind tunnel. Through the analysis of the drag force and resultant force angle, we proved that the integrity of feathers, whose barbs are usually closely interconnected, played an important role in the drag, which potentially triggers excellent drag reduction performance. The wind tunnel tests indicated that intact secondary feathers had a surprisingly high maximum drag reduction property at v?=?9 m/s compared with the feathers, where the integrity of barbs was damaged. The hook cascades facilitated elasticity under pressure and suitable permeability in an intact feather, when the hooks were interlocked. It was indicated that the suitable permeability of intact feathers would prevent flow separation and reduce drag force at low wind speed; at high wind speed, elasticity under pressure and suitable permeability in an intact feather would facilitate strong squeezing effect, helping feathers withstand larger aerodynamic forces to which they might be subjected during flight. It was revealed that the intact secondary feather is a compromise between strong lift generation and drag reduction, which has a great significance for the bird’s flight.

关键词: Morphological integrity , · Secondary feather , · Drag reduction , · Wind tunnel , · Smoke visualization , · Bioinspiration

Abstract: Flight feathers of birds interact with the air flow during flight. How the observed low drag and high lift values at wind speeds from 9.0 to 19.8 m/s can be achieved due to the feather aerodynamics remains unknown. In the present paper, we tested and compared morphological changes, drag reduction and flow visualization results of intact, damaged, and artificial feathers at different wind speeds in a wind tunnel. Through the analysis of the drag force and resultant force angle, we proved that the integrity of feathers, whose barbs are usually closely interconnected, played an important role in the drag, which potentially triggers excellent drag reduction performance. The wind tunnel tests indicated that intact secondary feathers had a surprisingly high maximum drag reduction property at v?=?9 m/s compared with the feathers, where the integrity of barbs was damaged. The hook cascades facilitated elasticity under pressure and suitable permeability in an intact feather, when the hooks were interlocked. It was indicated that the suitable permeability of intact feathers would prevent flow separation and reduce drag force at low wind speed; at high wind speed, elasticity under pressure and suitable permeability in an intact feather would facilitate strong squeezing effect, helping feathers withstand larger aerodynamic forces to which they might be subjected during flight. It was revealed that the intact secondary feather is a compromise between strong lift generation and drag reduction, which has a great significance for the bird’s flight.

Key words: Morphological integrity , · Secondary feather , · Drag reduction , · Wind tunnel , · Smoke visualization , · Bioinspiration